<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>strict - Perl pragma to restrict unsafe constructs - Perldoc Browser</title>
    <link rel="search" href="https://perldoc.perl.org/opensearch.xml" type="application/opensearchdescription+xml" title="Perldoc Browser">
    <link rel="canonical" href="https://perldoc.perl.org/strict">
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css" integrity="sha384-JcKb8q3iqJ61gNV9KGb8thSsNjpSL0n8PARn9HuZOnIxN0hoP+VmmDGMN5t9UJ0Z" crossorigin="anonymous">
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/10.5.0/styles/stackoverflow-light.min.css" integrity="sha512-cG1IdFxqipi3gqLmksLtuk13C+hBa57a6zpWxMeoY3Q9O6ooFxq50DayCdm0QrDgZjMUn23z/0PMZlgft7Yp5Q==" crossorigin="anonymous" />
    <style>
      body {
        background: #f4f4f5;
        color: #020202;
      }
      .navbar-dark {
        background-image: -webkit-linear-gradient(top, #005f85 0, #002e49 100%);
        background-image: -o-linear-gradient(top, #005f85 0, #002e49 100%);
        background-image: linear-gradient(to bottom, #005f85 0, #002e49 100%);
        filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#ff005f85', endColorstr='#ff002e49', GradientType=0);
        background-repeat: repeat-x;
      }
      .navbar-dark .navbar-nav .nav-link,
      .navbar-dark .navbar-nav .nav-link:focus { color: #fff }
      .navbar-dark .navbar-nav .nav-link:hover { color: #ffef68 }
      #wrapperlicious {
        margin: 0 auto;
        font: 0.9em 'Helvetica Neue', Helvetica, sans-serif;
        font-weight: normal;
        line-height: 1.5em;
        margin: 0;
        padding: 0;
      }
      #wrapperlicious h1 { font-size: 1.5em }
      #wrapperlicious h2 { font-size: 1.3em }
      #wrapperlicious h3 { font-size: 1.1em }
      #wrapperlicious h4 { font-size: 0.9em }
      #wrapperlicious h1, #wrapperlicious h2, #wrapperlicious h3,
      #wrapperlicious h4, #wrapperlicious dt {
        color: #020202;
        margin-top: 1em;
        margin-bottom: 1em;
        position: relative;
        font-weight: bold;
      }
      #wrapperlicious a { color: inherit; text-decoration: underline }
      #wrapperlicious #toc { text-decoration: none }
      #wrapperlicious a:hover { color: #2a2a2a }
      #wrapperlicious a img { border: 0 }
      #wrapperlicious :not(pre) > code {
        color: inherit;
        background-color: rgba(0, 0, 0, 0.04);
        border-radius: 3px;
        font: 0.9em Consolas, Menlo, Monaco, monospace;
        padding: 0.3em;
      }
      #wrapperlicious dd {
        margin: 0;
        margin-left: 2em;
      }
      #wrapperlicious dt {
        color: #2a2a2a;
        font-weight: bold;
        margin-left: 0.9em;
      }
      #wrapperlicious p {
        margin-bottom: 1em;
        margin-top: 1em;
      }
      #wrapperlicious li > p {
        margin-bottom: 0;
        margin-top: 0;
      }
      #wrapperlicious pre {
        border: 1px solid #c1c1c1;
        border-radius: 3px;
        font: 100% Consolas, Menlo, Monaco, monospace;
        margin-bottom: 1em;
        margin-top: 1em;
      }
      #wrapperlicious pre > code {
        display: block;
        background-color: #f6f6f6;
        font: 0.9em Consolas, Menlo, Monaco, monospace;
        line-height: 1.5em;
        text-align: left;
        white-space: pre;
        padding: 1em;
      }
      #wrapperlicious dl, #wrapperlicious ol, #wrapperlicious ul {
        margin-bottom: 1em;
        margin-top: 1em;
      }
      #wrapperlicious ul {
        list-style-type: square;
      }
      #wrapperlicious ul ul {
        margin-bottom: 0px;
        margin-top: 0px;
      }
      #footer {
        font-size: 0.8em;
        padding-top: 0.5em;
        text-align: center;
      }
      #more {
        display: inline;
        font-size: 0.8em;
      }
      #perldocdiv {
        background-color: #fff;
        border: 1px solid #c1c1c1;
        border-bottom-left-radius: 5px;
        border-bottom-right-radius: 5px;
        margin-left: auto;
        margin-right: auto;
        padding: 3em;
        padding-top: 1em;
        max-width: 960px;
      }
      #moduleversion { float: right }
      #wrapperlicious .leading-notice {
        font-style: italic;
        padding-left: 1em;
        margin-top: 1em;
        margin-bottom: 1em;
      }
      #wrapperlicious .permalink {
        display: none;
        left: -0.75em;
        position: absolute;
        padding-right: 0.25em;
        text-decoration: none;
      }
      #wrapperlicious h1:hover .permalink, #wrapperlicious h2:hover .permalink,
      #wrapperlicious h3:hover .permalink, #wrapperlicious h4:hover .permalink,
      #wrapperlicious dt:hover .permalink {
        display: block;
      }
    </style>
    <!-- Global site tag (gtag.js) - Google Analytics -->
    <script async src="https://www.googletagmanager.com/gtag/js?id=G-KVNWBNT5FB"></script>
    <script>
      window.dataLayer = window.dataLayer || [];
      function gtag(){dataLayer.push(arguments);}
      gtag('js', new Date());

      gtag('config', 'G-KVNWBNT5FB');
      gtag('config', 'UA-50555-3');
    </script>
  </head>
  <body>
    <nav class="navbar navbar-expand-md navbar-dark bg-dark justify-content-between">
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  </button>
  <a class="navbar-brand" href="https://perldoc.perl.org/">Perldoc Browser</a>
  <div class="collapse navbar-collapse" id="navbarNav">
    <ul class="navbar-nav mr-auto">
      <li class="nav-item dropdown text-nowrap">
        <a class="nav-link dropdown-toggle" href="strict.html#" id="dropdownlink-stable" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">5.35.0</a>
        <div class="dropdown-menu" aria-labelledby="dropdownlink-stable">
          <a class="dropdown-item" href="https://perldoc.perl.org/strict">Latest</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.38.2/strict">5.38.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.38.1/strict">5.38.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.38.0/strict">5.38.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.36.3/strict">5.36.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.36.2/strict">5.36.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.36.1/strict">5.36.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.36.0/strict">5.36.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.34.3/strict">5.34.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.34.2/strict">5.34.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.34.1/strict">5.34.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.34.0/strict">5.34.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.32.1/strict">5.32.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.32.0/strict">5.32.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.30.3/strict">5.30.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.30.2/strict">5.30.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.30.1/strict">5.30.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.30.0/strict">5.30.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.28.3/strict">5.28.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.28.2/strict">5.28.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.28.1/strict">5.28.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.28.0/strict">5.28.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.26.3/strict">5.26.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.26.2/strict">5.26.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.26.1/strict">5.26.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.26.0/strict">5.26.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.24.4/strict">5.24.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.24.3/strict">5.24.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.24.2/strict">5.24.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.24.1/strict">5.24.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.24.0/strict">5.24.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.22.4/strict">5.22.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.22.3/strict">5.22.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.22.2/strict">5.22.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.22.1/strict">5.22.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.22.0/strict">5.22.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.20.3/strict">5.20.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.20.2/strict">5.20.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.20.1/strict">5.20.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.20.0/strict">5.20.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.18.4/strict">5.18.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.18.3/strict">5.18.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.18.2/strict">5.18.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.18.1/strict">5.18.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.18.0/strict">5.18.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.16.3/strict">5.16.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.16.2/strict">5.16.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.16.1/strict">5.16.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.16.0/strict">5.16.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.14.4/strict">5.14.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.14.3/strict">5.14.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.14.2/strict">5.14.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.14.1/strict">5.14.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.14.0/strict">5.14.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.12.5/strict">5.12.5</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.12.4/strict">5.12.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.12.3/strict">5.12.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.12.2/strict">5.12.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.12.1/strict">5.12.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.12.0/strict">5.12.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.10.1/strict">5.10.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.10.0/strict">5.10.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.9/strict">5.8.9</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.8/strict">5.8.8</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.7/strict">5.8.7</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.6/strict">5.8.6</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.5/strict">5.8.5</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.4/strict">5.8.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.3/strict">5.8.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.2/strict">5.8.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.1/strict">5.8.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.0/strict">5.8.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.6.2/strict">5.6.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.6.1/strict">5.6.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.6.0/strict">5.6.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.005_04/strict">5.005_04</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.005_03/strict">5.005_03</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.005_02/strict">5.005_02</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.005_01/strict">5.005_01</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.005/strict">5.005</a>
        </div>
      </li>
      <li class="nav-item dropdown text-nowrap">
        <a class="nav-link dropdown-toggle" href="strict.html#" id="dropdownlink-dev" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Dev</a>
        <div class="dropdown-menu" aria-labelledby="dropdownlink-dev">
          <a class="dropdown-item" href="https://perldoc.perl.org/blead/strict">blead</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.39.6/strict">5.39.6</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.39.5/strict">5.39.5</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.39.4/strict">5.39.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.39.3/strict">5.39.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.39.2/strict">5.39.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.39.1/strict">5.39.1</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.38.0-RC2/strict">5.38.0-RC2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.38.0-RC1/strict">5.38.0-RC1</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.11/strict">5.37.11</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.10/strict">5.37.10</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.9/strict">5.37.9</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.8/strict">5.37.8</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.7/strict">5.37.7</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.6/strict">5.37.6</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.5/strict">5.37.5</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.4/strict">5.37.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.3/strict">5.37.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.2/strict">5.37.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.1/strict">5.37.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.0/strict">5.37.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.11/strict">5.35.11</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.10/strict">5.35.10</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.9/strict">5.35.9</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.8/strict">5.35.8</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.7/strict">5.35.7</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.6/strict">5.35.6</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.5/strict">5.35.5</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.4/strict">5.35.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.3/strict">5.35.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.2/strict">5.35.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.1/strict">5.35.1</a>
          <a class="dropdown-item active" href="strict.html">5.35.0</a>
        </div>
      </li>
      <li class="nav-item dropdown text-nowrap">
        <a class="nav-link dropdown-toggle" href="strict.html#" id="dropdownlink-nav" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Documentation</a>
        <div class="dropdown-menu" aria-labelledby="dropdownlink-nav">
          <a class="dropdown-item" href="perl.html">Perl</a>
          <a class="dropdown-item" href="perlintro.html">Intro</a>
          <a class="dropdown-item" href="perl.html#Tutorials">Tutorials</a>
          <a class="dropdown-item" href="perlfaq.html">FAQs</a>
          <a class="dropdown-item" href="perl.html#Reference-Manual">Reference</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="perlop.html">Operators</a>
          <a class="dropdown-item" href="functions.html">Functions</a>
          <a class="dropdown-item" href="variables.html">Variables</a>
          <a class="dropdown-item" href="modules.html">Modules</a>
          <a class="dropdown-item" href="perlutil.html">Utilities</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="perlcommunity.html">Community</a>
          <a class="dropdown-item" href="perlhist.html">History</a>
        </div>
      </li>
    </ul>
    <ul class="navbar-nav">
      <script>
        function set_expand (expand) {
          var perldocdiv = document.getElementById('perldocdiv');
          var width = window.getComputedStyle(perldocdiv).getPropertyValue('max-width');
          var expanded = (width == '' || width == 'none') ? true : false;
          if (expand === null) {
            expand = !expanded;
          }
          if ((expand && !expanded) || (!expand && expanded)) {
            perldocdiv.style.setProperty('max-width', expand ? 'none' : '960px');
            var button_classlist = document.getElementById('content-expand-button').classList;
            if (expand) {
              button_classlist.add('btn-light');
              button_classlist.remove('btn-outline-light');
            } else {
              button_classlist.add('btn-outline-light');
              button_classlist.remove('btn-light');
            }
          }
          return expand;
        }
        function toggle_expand () {
          var expand = set_expand(null);
          document.cookie = 'perldoc_expand=' + (expand ? 1 : 0) + '; path=/; expires=Tue, 19 Jan 2038 03:14:07 UTC';
        }
        function read_expand () {
          return document.cookie.split(';').some(function (item) { return item.indexOf('perldoc_expand=1') >= 0 });
        }
        if (document.readyState === 'loading') {
          document.addEventListener('DOMContentLoaded', function () {
            if (read_expand()) {
              set_expand(true);
            }
          });
        } else if (read_expand()) {
          set_expand(true);
        }
      </script>
      <button id="content-expand-button" type="button" class="btn btn-outline-light d-none d-lg-inline-block mr-2" onclick="toggle_expand()">Expand</button>
    <ul>
    <form class="form-inline" method="get" action="https://perldoc.perl.org/5.35.0/search">
      <input class="form-control mr-3" type="search" name="q" placeholder="Search" aria-label="Search">
    </form>
  </div>
</nav>

    <div id="wrapperlicious" class="container-fluid">
      <div id="perldocdiv">
        <div id="links">
          <a href="strict.html">strict</a>
          <div id="more">
            (<a href="strict.txt">source</a>,
            <a href="https://metacpan.org/pod/strict">CPAN</a>)
          </div>
            <div id="moduleversion">version 1.12</div>
        </div>
        <div class="leading-notice">
          You are viewing the version of this documentation from Perl 5.35.0.
            This is a development version of Perl.
        </div>
        <h1><a id="toc">CONTENTS</a></h1>
                  <ul>
              <li>
                <a class="text-decoration-none" href="strict.html#NAME">NAME</a>
              </li>
              <li>
                <a class="text-decoration-none" href="strict.html#SYNOPSIS">SYNOPSIS</a>
              </li>
              <li>
                <a class="text-decoration-none" href="strict.html#DESCRIPTION">DESCRIPTION</a>
              </li>
              <li>
                <a class="text-decoration-none" href="strict.html#HISTORY">HISTORY</a>
              </li>
          </ul>

      <h1 id="NAME"><a class="permalink" href="strict.html#NAME">#</a>NAME</h1>

<p>strict - Perl pragma to restrict unsafe constructs</p>

<h1 id="SYNOPSIS"><a class="permalink" href="strict.html#SYNOPSIS">#</a>SYNOPSIS</h1>

<pre><code>use strict;

use strict &quot;vars&quot;;
use strict &quot;refs&quot;;
use strict &quot;subs&quot;;

use strict;
no strict &quot;vars&quot;;</code></pre>

<h1 id="DESCRIPTION"><a class="permalink" href="strict.html#DESCRIPTION">#</a>DESCRIPTION</h1>

<p>The <code>strict</code> pragma disables certain Perl expressions that could behave unexpectedly or are difficult to debug, turning them into errors. The effect of this pragma is limited to the current file or scope block.</p>

<p>If no import list is supplied, all possible restrictions are assumed. (This is the safest mode to operate in, but is sometimes too strict for casual programming.) Currently, there are three possible things to be strict about: &quot;subs&quot;, &quot;vars&quot;, and &quot;refs&quot;.</p>

<dl>

<dt id="strict-refs"><a class="permalink" href="strict.html#strict-refs">#</a><a id="strict"></a><code>strict refs</code></dt>
<dd>

<p>This generates a runtime error if you use symbolic references (see <a href="perlref.html">perlref</a>).</p>

<pre><code>use strict &#39;refs&#39;;
$ref = \$foo;
print $$ref;	# ok
$ref = &quot;foo&quot;;
print $$ref;	# runtime error; normally ok
$file = &quot;STDOUT&quot;;
print $file &quot;Hi!&quot;;	# error; note: no comma after $file</code></pre>

<p>There is one exception to this rule:</p>

<pre><code>$bar = \&amp;{&#39;foo&#39;};
&amp;$bar;</code></pre>

<p>is allowed so that <code>goto &amp;$AUTOLOAD</code> would not break under stricture.</p>

</dd>
<dt id="strict-vars"><a class="permalink" href="strict.html#strict-vars">#</a><a id="strict1"></a><code>strict vars</code></dt>
<dd>

<p>This generates a compile-time error if you access a variable that was neither explicitly declared (using any of <code>my</code>, <code>our</code>, <code>state</code>, or <code>use vars</code>) nor fully qualified. (Because this is to avoid variable suicide problems and subtle dynamic scoping issues, a merely <code>local</code> variable isn&#39;t good enough.) See <a href="perlfunc.html#my">&quot;my&quot; in perlfunc</a>, <a href="perlfunc.html#our">&quot;our&quot; in perlfunc</a>, <a href="perlfunc.html#state">&quot;state&quot; in perlfunc</a>, <a href="perlfunc.html#local">&quot;local&quot; in perlfunc</a>, and <a href="vars.html">vars</a>.</p>

<pre><code>use strict &#39;vars&#39;;
$X::foo = 1;	 # ok, fully qualified
my $foo = 10;	 # ok, my() var
local $baz = 9;	 # blows up, $baz not declared before

package Cinna;
our $bar;			# Declares $bar in current package
$bar = &#39;HgS&#39;;		# ok, global declared via pragma</code></pre>

<p>The local() generated a compile-time error because you just touched a global name without fully qualifying it.</p>

<p>Because of their special use by sort(), the variables $a and $b are exempted from this check.</p>

</dd>
<dt id="strict-subs"><a class="permalink" href="strict.html#strict-subs">#</a><a id="strict2"></a><code>strict subs</code></dt>
<dd>

<p>This disables the poetry optimization, generating a compile-time error if you try to use a bareword identifier that&#39;s not a subroutine, unless it is a simple identifier (no colons) and that it appears in curly braces, on the left hand side of the <code>=&gt;</code> symbol, or has the unary minus operator applied to it.</p>

<pre><code>use strict &#39;subs&#39;;
$SIG{PIPE} = Plumber;   # blows up
$SIG{PIPE} = &quot;Plumber&quot;; # fine: quoted string is always ok
$SIG{PIPE} = \&amp;Plumber; # preferred form</code></pre>

</dd>
</dl>

<p>See <a href="perlmodlib.html#Pragmatic-Modules">&quot;Pragmatic Modules&quot; in perlmodlib</a>.</p>

<h1 id="HISTORY"><a class="permalink" href="strict.html#HISTORY">#</a>HISTORY</h1>

<p><code>strict &#39;subs&#39;</code>, with Perl 5.6.1, erroneously permitted to use an unquoted compound identifier (e.g. <code>Foo::Bar</code>) as a hash key (before <code>=&gt;</code> or inside curlies), but without forcing it always to a literal string.</p>

<p>Starting with Perl 5.8.1 strict is strict about its restrictions: if unknown restrictions are used, the strict pragma will abort with</p>

<pre><code class="plaintext">Unknown &#39;strict&#39; tag(s) &#39;...&#39;</code></pre>

<p>As of version 1.04 (Perl 5.10), strict verifies that it is used as &quot;strict&quot; to avoid the dreaded Strict trap on case insensitive file systems.</p>


      </div>
      <div id="footer">
        <p>Perldoc Browser is maintained by Dan Book (<a href="https://metacpan.org/author/DBOOK">DBOOK</a>). Please contact him via the <a href="https://github.com/Grinnz/perldoc-browser/issues">GitHub issue tracker</a> or <a href="mailto:dbook@cpan.org">email</a> regarding any issues with the site itself, search, or rendering of documentation.</p>

<p>The Perl documentation is maintained by the Perl 5 Porters in the development of Perl. Please contact them via the <a href="https://github.com/Perl/perl5/issues">Perl issue tracker</a>, the <a href="https://lists.perl.org/list/perl5-porters.html">mailing list</a>, or <a href="https://kiwiirc.com/client/irc.perl.org/p5p">IRC</a> to report any issues with the contents or format of the documentation.</p>


      </div>
    </div>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.slim.min.js" integrity="sha512-/DXTXr6nQodMUiq+IUJYCt2PPOUjrHJ9wFrqpJ3XkgPNOZVfMok7cRw6CSxyCQxXn6ozlESsSh1/sMCTF1rL/g==" crossorigin="anonymous"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.1/umd/popper.min.js" integrity="sha512-ubuT8Z88WxezgSqf3RLuNi5lmjstiJcyezx34yIU2gAHonIi27Na7atqzUZCOoY4CExaoFumzOsFQ2Ch+I/HCw==" crossorigin="anonymous"></script>
    <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/js/bootstrap.min.js" integrity="sha384-B4gt1jrGC7Jh4AgTPSdUtOBvfO8shuf57BaghqFfPlYxofvL8/KUEfYiJOMMV+rV" crossorigin="anonymous"></script>
    <script src="../highlight.pack.js"></script>
    <script>hljs.highlightAll();</script>
  </body>
</html>
